. Planaria can be cut into pieces, and each piece can regenerate into a complete organism. Cells at the location of the wound site proliferate to form a mass of cells that will differentiate into new tissues and regenerate the missing parts of the piece of the cut planaria.Very small pieces of the planarian, estimated to be as little as 1/279th of the organism it is cut from, can regenerate back into a complete organism over the course of a few weeks. New tissues can grow that have the ability to create all the various cell types.The organism itself does not have to be completely cut into separate pieces for the regeneration phenomenon to be witnessed. In fact, if the head of a planaria is cut in half down its centre, and each side retained on the organism, it is possible for the planaria to regenerate two heads and continue to live.